1. Field of the Invention
The present invention relates to a regenerating system for a filtering means for collecting particulates discharged from a diesel engine.
2. Description of the Related Art
As a system of this type, there has conventionally been known a system with a filtering means which comprises an oxidation catalyst for oxidizing NO in exhaust gas of a diesel engine into NO2 provided in an exhaust pipe of the engine, and a particulate filter for collecting particulates in exhaust gas passing through this exhaust pipe provided in the exhaust pipe on the exhaust gas downstream side of the oxidation catalyst.
In the filtering means regenerating system constructed in this manner, NO in exhaust gas of the engine is oxidized into NO2 by the oxidation catalyst, and particulates collected by the particulate filter are oxidized by this NO2 and removed in the exhaust gas temperature range above 250 to 300xc2x0 C., so that the particulate filter can be regenerated.
In the above-described conventional filtering means regenerating system, however, for example, in a case where a light-load operation is continued, the regeneration of the particulate filter becomes insufficient, and the particulate filter gradually becomes in an excessively collecting state, so that the exhaust gas pressure of the engine increases. Therefore, there is a fear of decreased fuel economy and power performance of the engine.
On the other hand, when an EGR system for recirculating some of exhaust gas of the engine to intake air is provided, the discharge amount of the particulates is increased by the increase in the exhaust gas pressure, and the EGR ratio increases, so that the amount of NO2 decreases, by which the regeneration effect of the particulate filter further decreases. Therefore, the excessively collecting state proceeds acceleratedly, so that there is a fear of rapidly decreased fuel economy and power performance of the engine.
Accordingly, an object of the present invention is to provide a filtering means regenerating system for a diesel engine, in which a particulate filter is prevented from becoming in an excessively collecting state in all operation statuses of the engine, by which the fuel economy and power performance of the engine can be prevented from decreasing.
In the first aspect of a regenerating system for a filtering means of the present invention, the filtering means is provided in an exhaust gas passage of a diesel engine to oxidize NO in exhaust gas of the engine into NO2, and to collect particulates in exhaust gas passing through the exhaust gas passage and to thereby oxidize the particulates by means of the NO2 and remove the same at a temperature higher than a predetermined exhaust gas temperature.
The present filtering means regenerating system comprises any one apparatus selected from a group consisting of a variable timer mechanism for an in-line fuel injection system or distributor type fuel injection system, which regulates either one or both of the injection timing and injection amount of fuel injected into the engine, an EGR valve of an EGR system, which controls the flow rate of exhaust gas recirculated from the exhaust gas passage to an intake air passage of the engine, a variable stator blade provided in a turbocharger for supercharging intake air in the intake air passage by means of energy of the exhaust gas to regulate the amount of intake air supercharged into the intake air passage, a variable valve timing mechanism for changing the opening/closing timing and lifts of an intake air valve and exhaust gas valve of the engine according to the operation status of the engine, and an intake air throttle valve provided in the intake air passage to control the opening of the intake air passage; deposit detecting means for detecting the deposit of particulates deposited on the filtering means; and a controller for controlling the selected one apparatus based on the detection output of the deposit detecting means.
In the filtering means regenerating system according to the first aspect of the invention, if the deposit detecting means detects a deposit of particulates larger than a predetermined amount on the filtering means, based on this detection output, the controller controls any one apparatus selected from a group consisting of the variable timer mechanism, the EGR valve, the variable stator blade, the variable valve timing mechanism, and the intake air throttle valve (for example, the variable timer mechanism) according to the operation status of the engine. At the time of low-load operation of the engine, the controller controls the variable timer mechanism to delay the injection timing of fuel as compared with the usual injection timing, so that the temperature of exhaust gas rises to a temperature at which the particulates can be oxidized by NO2 and removed. As a result, after NO in exhaust gas is oxidized into NO2 by the oxidation catalyst, the particulates deposited on the filtering means are rapidly oxidized by the NO2 and removed. On the other hand, at the time of high-load operation of the engine, the controller controls the variable timer mechanism to advance the injection timing of fuel as compared with the usual injection timing, so that the discharge amount of NO in exhaust gas increases. As a result, the amount of NO2 produced by the oxidation of NO using the oxidation catalyst is increased. Therefore, the particulates deposited on the filtering means are rapidly oxidized by this increased NO2 and removed.
In the second aspect of the present invention, a filtering means regenerating system comprises two or three or more apparatuses selected from a group consisting of a variable timer mechanism for an in-line fuel injection system or distributor type fuel injection system, which regulates either one or both of the injection timing and injection amount of fuel injected into an engine, an EGR valve of an EGR system, which controls the flow rate of exhaust gas recirculated from an exhaust gas passage to an intake air passage of the engine, a variable stator blade provided in a turbocharger for supercharging intake air in the intake air passage by means of energy of the exhaust gas to regulate the amount of intake air supercharged into the intake air passage, a variable valve timing mechanism for changing the opening/closing timing and lifts of an intake air valve and exhaust gas valve of the engine according to the operation status of the engine, an intake air throttle valve provided in the intake air passage to control the opening of the intake air passage, and an exhaust gas throttle valve provided in the exhaust gas passage to control the opening of the exhaust gas passage; deposit detecting means for detecting the deposit of particulates deposited on a filtering means; and a controller for controlling the selected two, three, or more apparatuses based on the detection output of the deposit detecting means.
In the filtering means regenerating system according to the second aspect of the invention, if the deposit detecting means detects a deposit of particulates larger than a predetermined amount on the particulate filter, based on this detection output, the controller controls two or three or more apparatuses selected from a group consisting of the variable timer mechanism, the EGR valve, the variable stator blade, the variable valve timing mechanism, the intake air throttle valve, and the exhaust gas throttle valve (for example, the variable timer mechanism, the EGR valve, the intake air throttle valve, and the exhaust gas throttle valve) according to the operation status of the engine. At the time of low-load operation of the engine, the controller controls the variable timer mechanism to delay the injection timing of fuel as compared with the usual injection timing, so that the temperature of exhaust gas is increased. Also, the controller decreases the opening of the EGR valve to decrease the EGR ratio, so that the discharge amount of NO is increased. Further, the controller throttles the intake air throttle valve and the exhaust gas throttle valve to decrease the air-fuel ratio and to increase the exhaust gas resistance, thereby increasing the discharge amount of NO and the temperature of exhaust gas.
On the other hand, at the time of high-load operation of the engine, the controller controls the variable timer mechanism to advance the injection timing of fuel as compared with the usual injection timing, so that the discharge amount of NO in exhaust gas is increased. Also, the controller decreases the opening of the EGR valve to increase the discharge amount of NO as described above, and further throttles the intake air throttle valve and the exhaust gas throttle valve to increase the discharge amount of NO and the temperature of exhaust gas as described above.
In the third aspect of the present invention, a filtering means regenerating system comprises one or two or more apparatuses selected from a group consisting of an accumulator fuel injection system, which regulates either one or both of the injection timing and injection amount of fuel injected into an engine, an EGR valve of an EGR system, which controls the flow rate of exhaust gas recirculated from an exhaust gas passage to an intake air passage of the engine, a variable stator blade provided in a turbocharger for supercharging intake air in the intake air passage by means of energy of the exhaust gas to regulate the amount of intake air supercharged into the intake air passage, a variable valve timing mechanism for changing the opening/closing timing and lifts of an intake air valve and exhaust gas valve of the engine according to the operation status of the engine, an intake air throttle valve provided in the intake air passage to control the opening of the intake air passage, and an exhaust gas throttle valve provided in the exhaust gas passage to control the opening of the exhaust gas passage; deposit detecting means for detecting the deposit of particulates deposited on a filtering means; and a controller for controlling the selected one, two, or more apparatuses based on the detection output of the deposit detecting means.
In the filtering means regenerating system according to the third aspect of the invention, if the deposit detecting means detects a deposit of particulates larger than a predetermined amount on the filtering means, based on this detection output, the controller controls one or two or more apparatuses selected from a group consisting of the accumulator fuel injection system, the EGR valve, the variable stator blade, the variable valve timing mechanism, the intake air throttle valve, and the exhaust gas throttle valve (for example, the accumulator fuel injection system) according to the operation status of the engine. At the time of low-load operation of the engine, the controller controls the accumulator fuel injection system to delay the injection timing of fuel as compared with the usual injection timing and to increase the injection amount of post-injection, so that the temperature of exhaust gas rises to a temperature at which the particulates can be oxidized by NO2 and removed. As a result, after NO in exhaust gas is oxidized into NO2 by the oxidation catalyst, the particulates deposited on the filtering means are rapidly oxidized by the NO2 and removed. On the other hand, at the time of high-load operation of the engine, the controller controls the accumulator fuel injection system to advance the injection timing of fuel as compared with the usual injection timing, so that the discharge amount of NO in exhaust gas increases. As a result, the amount of NO2 produced by the oxidation of NO using the oxidation catalyst is increased. Therefore, the particulates deposited on the filtering means are rapidly oxidized by this increased NO2 and removed.
Preferably, the aforementioned deposit detecting means is configured by one or two or more sensors selected from a group consisting of an exhaust gas pressure sensor for detecting the pressure of exhaust gas, an engine rotation sensor for detecting the rotational speed of the engine, an engine load sensor for detecting the load of the engine, an engine operation timer for detecting the operation time of the engine, an intake air amount sensor for detecting the amount of intake air of the engine, an NOx sensor for detecting the concentration of NOx in exhaust gas, an O2 sensor for detecting the concentration of oxygen contained in the exhaust gas, and an exhaust gas temperature sensor for detecting the temperature of the exhaust gas.